Worldwide energy demand, particularly for fossil fuels, is rising as populations increase and nations develop. Concurrently, concerns regarding climate change, declining fossil fuel reserves, and national security have moved to the forefront of society. These concerns have largely arisen due to unpredictable energy costs as well as a greater understanding of the effects of burning fossil fuels and the emissions released therefrom. Individuals and countries alike are searching for alternative energy sources that may supplement or even replace fossil fuels. Biodiesel is being explored as one promising alternative energy source.
Biodiesel is a liquid fuel composed of fatty acid alkyl esters generally derived from biomass feedstocks that contain lipids (e.g., triacylglycerides). Biodiesel can be classified based on the feedstock used to produce it. First-generation biodiesel is typically produced from edible biomass containing oils such as soybeans and canola. Generally, the edible biomass is harvested and dried, the oil is extracted using organic solvents (e.g., hexane), and the oils are transesterified into biodiesel. These terrestrial crops require large amounts of arable land, freshwater, fertilizers, and must be allocated from food production to fuel production therefore leading to a competition of “fuel vs. food.” Second-generation biodiesels are produced from non-edible biomass feedstocks, such as jatropha, and utilize a similar method of preparation as first generation biodiesels. Third-generation biodiesel generally refers to the use of algae as a feedstock.
Although promising, the use of wet biomass such as algae to produce biodiesel is complicated by their cultivation in dilute aqueous suspensions. Furthermore, existing processes for producing biodiesel from algae generally require energy and cost intensive dewatering steps, processing steps, and long production times.
Accordingly, there remains an opportunity to develop a method of producing biodiesel from a wet biomass to minimize the cost and environmental impact of biomass processing, dewatering, and oil conversion to biodiesel while maximizing production efficiencies.